Lewis rats severely depleted of T cells (Lewis B rats) and Lewis-BNF1 hybrids are resistant to experimental allergic encephalomyelitis. These animals reconstituted with thymocytes regain their ability to respond to an encephalitogenic challenge. The cellular requirements for the conversion of the EAE resistant B rat into a sensitive recipient will be more precisely studied. Both active immunizations and passive transfer experiments will be conducted. Fractionated cell populations (B,T) obtained with various methods will be used for passive transfer and reconstitution experiments. The neuronal plasma membrane "receptor" to various specific ligands will be explored. The site(s) of adsorptive endocytosis of neuronal membrane "receptor" ligand complexes will be investigated. The following ligands will be used: lectins, antiglycosyl antibodies, anti-fetuin antibodies, cholera toxin and nerve growth factor. The following in vitro neuronal culture systems will be used: organotypic CNS cultures, dispersed CNS cultures, and murine neuroblastoma.